The inventive concepts disclosed herein relate generally to the field of antennas. More particularly, embodiments of the inventive concepts disclosed herein relate to a switched reluctance antenna for transmitting very low frequency and ultra low frequency radio signals.
Existing antennas for low frequency transmissions are generally impractical because of the required antenna size. To efficiently generate very low frequency radiation has required an antenna subtending a large fraction of a wavelength, extending thousands of feet. For example, a 1 kHz transmission has a corresponding wavelength of 300 km, indicating a general size range for an antenna producing such a transmission. While some airborne platforms have been developed to incorporate a trailing antenna having a length of approximately five miles, such a design would not be feasible for most applications, including ground-based antennas. In addition, electrically small antennas (e.g., having a size dimension corresponding to one tenth of the desired carrier frequency) have relatively low radiation resistance, and thus have poor efficiency due to ohmic losses resulting from the relatively great excitation currents required to overcome the radiation resistance, making electrically small antennas ineffective for low frequency transmissions.